Maintaining seed quality during storage is important for seed industry and farmers. Seed ageing is inevitable during storage and results in loss of vigour and germination. The rate of ageing is influenced by storage conditions and genetic factors. The deterioration is the result of accumulation of damage mainly by oxidation reactions, and the rate is increased by high temperature, moisture and oxygen levels. To estimate longevity in general CD tests are used with high moist and temperature to speed up deterioration. However, the results of these test often show poor correlation with long-term storage under dry conditions. This is mainly due to differences in the physiology of seeds at different water activity under these two ageing conditions. Previous research by our group has shown that for several crops seed ageing under dry conditions can be accelerated by storing at an elevated partial pressure of oxygen (EPPO). Also with rice, seed ageing can be accelerated by storing seeds under high oxygen levels (EPPO). Rice seed lots from different varieties showed variation in their tolerance to 5wk EPPO ageing at water activity of 0.4 and 35°C. EPPO aged rice seeds show both loss of germination over storage time and reduced vigour with slower germination.

Vigour loss during seed storage is often accompanied with a decline in oxidative respiration activity after imbibition due to mitochondrial damage. Poor functioning of the mitochondria will result in ethanol production. Indeed, upon imbibition EPPO aged rice seeds produced more ethanol, compared to seeds stored for the same time under lab conditions, upon imbibition. Rice seed lots with low tolerance to EPPO ageing produced more ethanol in the assay than more tolerant seed lots. This indicates that EPPO aging results in more mitochondrial damage and that part of the variation between seed lots (and potentially genotypes) is in the tolerance towards the induction of oxidative damage.

In conclusion, dry ageing of rice seeds under EPPO conditions shows the damaging effects of oxygen during storage, making it a potentially better method to study genetic variation for seed longevity in rice under dry storage conditions than a traditional CD test.

Speaker:

Steven Groot
Researcher seed quality,
Wageningen University and Research centre, Plant Research International